Cognitive Decline Related to Site-Specific Mid-Life Adiposity

Changes in central adiposity correlate with cognitive performance later in life.

Increasing waist circumference in midlife increases the risk of cognitive decline in late life, according to research published in the Journal of the American Geriatric Society. In a multicenter study of African Americans, changes to central adiposity — but not adiposity in general — showed a direct correlation with later cognitive performance.

Investigators from multiple geriatric departments in the United States retrospectively evaluated data collected from 1108 African American participants in the Genetic Epidemiology Network in Arteriopathy (GENOA) study of hypertension conducted in Jackson, Mississippi. The first visits for cognitive testing occurred between 1997 and 1999, with follow-up visits between 2001 and 2006 (visit 2) and 2009 and 2011 (visit 3). Midlife ages ranged from 35 to 59 and late life was defined as older than 60. Adiposity was measured at visits 1 and 2. “We didn't have the data to look at weight patterns before midlife, nor did we have data on duration of obesity,” study co-investigator Nancy West, PhD, of the department of preventive medicine at the John D. Bower School of Population Health /The MIND Center at the University of Mississippi Medical Center in Jackson, told Neurology Advisor.

Changes in waist circumference measured at visit 2 showed an inverse relationship to cognitive Z-scores (representing a composite of multiple cognitive evaluation scores) at visit 3: increases in weight ≥5% corresponded with lower Z-scores, while decreases ≥5% corresponded with higher Z-scores. This pattern reversed in late life, when decreases in waist circumference were associated with lower Z-scores.

Changes to total body weight measured by body mass index (BMI) at visit 2, however, did not influence later cognition. “In our study, there was no relationship between BMI at midlife and cognitive decline,” Dr West said, although decreases to BMI in late life were associated with lower Z-scores. Stable BMI across the lifespan indicated significantly higher mean Z-scores compared with the weight-gain group at midlife and compared with the weight-loss group in late life.

The prevalence of cardiovascular risk factors in the study population was of particular interest, as African Americans are disproportionally affected by both obesity and late-onset dementia.2,3 “Our study provides some evidence that, in addition to central obesity being a risk factor for heart disease (as has been shown in other studies), it may also be a risk factor [for] cognitive decline as well,” Dr West said.

Although the patterns were clear, the reasons for changing risk over a lifetime trajectory of weight gain or loss were not. The investigators suggested that, “something inherent to central adiposity may increase the risk of cognitive decline,” and pointed to a number of mechanisms, including brain volume changes associated with adiposity and inflammation, as further areas of study.

The study was limited by a lack of evaluation of dementia in the GENOA patient base, providing softer outcomes of cognitive decline for the current study measures. The use of a specific population of African Americans with hypertension from a single location suggests that the findings may not be generalizable to other populations.